More evidence for an alien megastructure?

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Mirannan

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Just released today, a paper suggesting (needs checking, of course) that a star which has already attracted attention has significantly dimmed over a span of several years:

https://arxiv.org/pdf/1608.01316v1.pdf

Scientists seem to be bending over backwards to find a non-sapient explanation for this. And are failing. Incidentally, the star is an F-type and they don't normally behave like that.
 
If it is a Dyson Sphere being constructed then the light curve should show a gradual dim, then a quick rise as the partially-completed net rotates away. The curve would return to the usual pattern until the net rotates back into view.
If it is being actively constructed, then over the course of time (say, 100 years), researchers would notice the curve dropping for longer periods, and then regular curve lasting for shorter periods. Eventually you would either see a period of time where the light curve is flat or barely angled down to 0 lux.
 
I'm no star at understanding stars.... but has anyone thought about the possibility that Tabby's star might be in some form of violent death throes?

I can think of another explanation (other than aliens building megastructures and roaming dark death/dead stars intervening in the line of sight to the Tabby's star), but I'd like to save that for a science fiction story.

Hey! Since when did I become a stellar world-builder?
 
I don't think anyone is bending over backwards, the simple fact is the presence of an alien megastructure doesn't make sense as a first conclusion. If it turned out to true, we would then be in the more difficult position of figuring out WHY so many other observations are what they are. Whenever you are considering a new result, you have to look at the already collected data to make an informed conclusion.

I'm referring in particular to the Fermi Paradox, the key points of which is this: given the number of stars in the galaxy, the very brief time it takes for intelligent life to evolve, and the amount of time that has passed since the first planets, we should expect to see a proliferation of alien structures, if in fact any other lifeforms anywhere in the galaxy has ever achieved interstellar travel. It took life on earth 3.5 billion years to produce humans, and all of modern human technology (including rudimentary interplanetary travel) can be summarized in just 3,000 years. If/once we reach interstellar capabilities, the amount of ground we can cover in a few thousand years is mind boggling, let alone a million or billion years.

The oldest observed exoplanet is 12.8 billions years old, so we know the planetary phase of our universe began way before Earth came around, so where the heck is everyone? Only one single planets would need to have reached near-future tech in the last 12 billion years to have populated the whole galaxy by now.

The fermi paradox is far from a certainty, and there are arguments against it, but it is generally consistent with our understanding of the timescales involved, the processes involved, and the dynamics of population expansion. That being the case, it would be very hard to explain ONE megastructure around one star when we haven't already seen tons of them all over the place. Doesn't mean it can't happen, but it is one reason why it doesn't make sense as a first conclusion.
 
Also, I don't see any "bending over backwards" in the article itself. They propose two simple transit models which are often associated with this type of event, and eliminate them as explanations, then they propose a perfectly reasonable, albeit more complicated model, that does explain the overall pattern:

...the spreading of debris along its orbit after a recent collision or the precession of an occulting disk into our line of sight could perhaps explain the appearance of a transit.... such a cloud would then need to be extended over a fraction of its Keplerian orbit and would need to maintain an approximately constant density through its entire length as it passes in front of this star.... Broadly speaking, the morphology of the light curve is generally consistent with the transit of a cloud of optically thick material orbiting the star. Such a dust cloud could be small enough to evade submillimeter detection
Click to expand...

To jump from that conclusion to say they are failing to provide a non-sapient explanation is a little misleading. There are all kinds of things going on around stars, we see new types of phenomena constantly. Maybe one day it will be an alien structure, who knows. This doesn't look like it to me, though.
 
zmunkz said:
I don't think anyone is bending over backwards, the simple fact is the presence of an alien megastructure doesn't make sense as a first conclusion. If it turned out to true, we would then be in the more difficult position of figuring out WHY so many other observations are what they are. Whenever you are considering a new result, you have to look at the already collected data to make an informed conclusion.

I'm referring in particular to the Fermi Paradox, the key points of which is this: given the number of stars in the galaxy, the very brief time it takes for intelligent life to evolve, and the amount of time that has passed since the first planets, we should expect to see a proliferation of alien structures, if in fact any other lifeforms anywhere in the galaxy has ever achieved interstellar travel. It took life on earth 3.5 billion years to produce humans, and all of modern human technology (including rudimentary interplanetary travel) can be summarized in just 3,000 years. If/once we reach interstellar capabilities, the amount of ground we can cover in a few thousand years is mind boggling, let alone a million or billion years.

The oldest observed exoplanet is 12.8 billions years old, so we know the planetary phase of our universe began way before Earth came around, so where the heck is everyone? Only one single planets would need to have reached near-future tech in the last 12 billion years to have populated the whole galaxy by now.

The fermi paradox is far from a certainty, and there are arguments against it, but it is generally consistent with our understanding of the timescales involved, the processes involved, and the dynamics of population expansion. That being the case, it would be very hard to explain ONE megastructure around one star when we haven't already seen tons of them all over the place. Doesn't mean it can't happen, but it is one reason why it doesn't make sense as a first conclusion.
Click to expand...

Taking the example of megastructures, Dyson swarms in this case: It might simply be that there are such objects all over the Galaxy but this is the only one, within range of our sensors, which is in the process of being built. Which isn't unreasonable, given that compared to the lifespan of a star the construction time of such an object is trivial.

"Ah", you say, "but what about all the others already built?" The answer to that is brutally simple; we haven't looked.

What would a completed Dyson swarm look like, after all? Answer; an object with the same luminosity as a main-sequence star, but all in the far infrared - a black body temperature of about 300K, if the people who built it were adapted to conditions like ours. Such an object would be far from obvious, unless one was looking specifically for it.

It might also be that the builders were sufficiently paranoid to hide it, by building a second shell and making use of the waste heat; the outer shell would radiate at maybe 50K, and I confess to not knowing whether we would ever find such an object, even if we looked.
 
Now, don't get me wrong here fellas, I know this is a Sci Fi forum and we are all a little fanciful -- but this Dyson Sphere business is a bit ridiculous. I mean, just look at a couple size charts of the Sun compared to the other planets ... where would a hypothetical race find an abundance of hypothetical material to enshroud (or partial enshroud) a star? What price in resources is to be paid to accomplish such a task and is that price even attainable?

I enjoy a good story like all you folks do -- but you way as well say GOD is passing his hand between the celestial body and Earth causing it to flicker. It makes about as much scientific sense.
 
Cathbad said:
Well, duh!! That's where the conquest and mine-stripping of other races' planets comes in!!

;)
Click to expand...

LOL, very true tho I don't know if you could call it strip mining if you essentially bag up the entire planet -- perhaps solar system -- for materials. I guess the guy manning the wheel of the Death Star better get an extra-large cup of coffee, he's working a triple shift.
 
Seems to me the big problem with the orbiting megastructure argument is that, just like a planet, the dimming would occur regularly which isn't the case.
 
Vertigo said:
Seems to me the big problem with the orbiting megastructure argument is that, just like a planet, the dimming would occur regularly which isn't the case.
Click to expand...

I'm not so sure. Wouldn't a regular occurrence require a stable orbit and speed?
 
With a Dyson swarm it is certainly possible that they might move around but surely not enough to give the wildly erratic sequence that has been observed:

But this star seemed to have two small dips in 2009, a large, weirdly asymmetric dip lasting a week in 2011 and a series of many dips during three months in 2013, some reducing the brightness of the star by as much as 20 per cent.
Click to expand...

I mean that would take some coordinated movements of such a swarm on a massive scale.

I think the idea of something like a very dense Kuiper belt with significant variations in that density and taking hundreds of years to orbit (the orbital period of Pluto in our Kuiper belt is around 250 years) would explain all the features especially if you added one or two massive objects into the mix that would accumulate a higher density of the smaller objects in their Trojan points. If this hypothetical Kuiper belt were even farther out than ours then it would take even longer than 250 years for a full cycle to be observed. IE longer than we currently have data in this case.
 
Well that's rather pleasing; not so different from the possible explanation I put forward including the asteroids in the leading and trailing Trojans. :D
 
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